As a result of the fast growing population, the worldwide energy demand and environmental safety has been a major concern resulting to a need for an environmental friendly source of energy. The energy sector is a key factor in the generation of greenhouse gases, majorly carbon dioxide and methane. Energy generation through renewable energy technologies releases minimal or no GHGs. Different alternative sources of energy have been discovered for various applications such as renewable energies. However, the universal use of a lot of these renewable sources is still at their premature stages due to their conversion rate which is not efficient enough (Trabelsi & Ben-Brahim 2011).
The demand and generation trends in the past years of energy policy is monitoring how people use energy and how energy use changes over time whereby electricity shareholders are finding it difficult to generate enough electricity that will meet the demand. In the past years, there have been significant changes in the electricity industry towards deregulation and completion with the aim of improving economic efficiency. There is competition among different firms to provide generation services at a price set by the market due to demand rate and communication between the firms. Analysis is also carried out by regulatory agencies to monitor and supervise market behaviour (Ventosa et al. 2005).
It is very important to plan for both the total energy required yearly and to ensure that generation capacity of energy generation is adequate and available at all times to meet the peak demand for power. The two available peaks in electricity consumption are the lower peak which occurs during early hours of the morning, and the other peak is greater, and sudden which arises late in the evening. These are predominantly caused by domestic activity at these times, and also due to plant start-ups in industries and commercial places. These peaks are seasonal, with the peak consumption occurring during winter period. In view of the different technologies and resources, it is therefore important to examine their capability to produce power when needed apart from their
ability to also generate a particular amount of energy over the year (Banks & Schaffler 2006).
Solar energy is regarded as one of the cleanest sources of energy resources that does not contribute to global warming. The sun radiates more energy in one second than what can be used by consumers from its time of existence. Solar energy is also known as alternative energy to fossil fuel energy sources such as oil, gas and coal. It is a cheap and abundant source of energy with less environmental hazards during the generation and conversion of energy. The gradual extinction of fossil fuels has given rise to interest in the integration of solar energy around the world (Solangi et al. 2011; Selvaraj & Rahim 2009).
Solar energy demand has increased over the past 20 years, at a steady rate of 20% to 25% per year as a result of the decreasing costs. Some of the reasons for the increase in the use of solar energy to generate electricity were identified as follows; improvement in the efficiency of solar cells; advanced manufacturing-technology; and economies of scale. 350 MW of solar equipment was sold in 2001 to complement the solar equipment producing a clean energy at this time. In addition, 574 MW of PV was installed in 2003. This increased to 927 MW the following year. The European Union was on a path to fulfilling its own goal of 3 GW of renewable energy from PV sources for 2010 (Carrasco et al. 2006).
Electricity demand by customers is getting higher. Therefore, there is the need for the most suitable technology which calls for further development of the PV system to contribute to the global electricity demand, resulting to the reduction in emission of carbon by decreasing the use of fossil plants. Terrestrial applications of PV market are; Consumer, Off-grid (mostly used in isolated industrial and developing countries for supplying the rural regions with electricity) and On-grid use (Hoffmann 2006). The key objective of having a storage capability in a grid connected system is to enable the system to function as an uninterruptible power supply to the loads when the utility grid cannot supply. During the day when there is excess energy generated, if a system lacks an energy storage, the excess energy will be sold back to the utility. The PV system without storage would not function during periods when there is no sunshine, therefore, limiting the overall utilization of the system to daytime periods. One usual way of increasing operation of the system is to model the DC to AC converter control to facilitate bidirectional flow of power and use the converter to supply reactive and harmonic compensation to the grid. When the PV is not capable of producing for a period, this function can still continue, as a result, system utilization is increased (Leslie 2003).
With the integration of the energy storage system(ESS) with the utility grid, the electricity produced at times of low demand and from intermittent renewable energy sources is shifted for times when the demand for electricity is high or when there is no other generation available. Adequate integration of the renewable energy sources with energy storage systems gives opportunity for higher market penetration (Serban &
Marinescu 2010; Carrasco et al. 2006).
The growing interest in the number of investors in solar energy has intensified the research that involves the development of a multifunctional inverter for stability of the grid. Solar photovoltaic technology could generate energy from the sun to provide large-scale, domestically safe, and global friendly electricity. Solar PV installation was projected to supply 15GW in 2010 as compared to 2.7GW in 2006. The need for silicon to produce solar cells is estimated to rise from 41,000 tons to 120,000 tons from 2006 to 2010 and an estimated increase of 400,000 tons in 2015. The Fig. 2.10 below shows the projected growth and installation of solar PV energy in some countries and worldwide till 2030.
Figure 2.10; Growth and installation of solar PV energy in various countries
The effect of PV in the electric power system is eventually limited by electricity demand that is not matching with normal solar PV production, resulting into unusable PV generation. In order not to incur so much cost by increasing the usefulness of solar PV
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generation, the electric power system will require modification to take in surplus production of solar PV.
the usefulness of this excess PV generation can be increased through some of the following ways (Denholm & Margolis 2007):
Increased flexibility: permits more of the normal load to be met by the PV by dropping the system minimum.
Load shifting: normal load to be deviated to periods of larger PV output.
Energy storage: electricity generated by solar to be stored and use of this stored energy at periods of minimal or no output by the solar.